1. Field of the Invention
This invention generally pertains to an air brake system, and more particularly a proportioning valve incorporating a double check valve, as used in an air brake system. It will be appreciated, however, that the invention may have broader applications and may be advantageously employed in related valve environments or braking applications.
2. Description of Related Art
A conventional brake proportioning assembly includes a housing or body having a blind end bore that receives a valve assembly. In the prior art, a spring, a nylon disk/spring follower, and a check valve of the valve assembly are inserted and manually held in place. The subassembly is inserted into the blind bore of the housing. The individual parts or components of the valve assembly are inadequately controlled and maintained in the proper orientation. Often times, it is not until the assembled valve is subsequently subjected to a pneumatic test that assembly problems are noticed.
Moreover, air flow control through the valve assembly is restricted. The dimensioning of the metal valve element restricts the size and number of openings that could be formed from machining operations. Although complex passages can be machined into the metal valve member, such machining ultimately makes the valve manufacturing cost prohibitive and still may not achieve the desired increase in air flow or improved flow profiles.
With conventional metal valve assemblies, only a limited amount of identifying indicia is provided on the valve components. It is desirable, however, and a goal of effective quality control procedure, to convey or record an increased amount of information on the valve itself without substantially increasing the cost to manufacture the valve assembly.